Optical fiber-delay line buffers with void filling

Details Optical fiber-delay line buffers with void filling Optical fiber-delay line buffers with void filling

1999-02-17

2002-12-10

Pascal, Leslie (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200, C359S199200, C359S199200, C359S199200, C359S199200

Reexamination Certificate

active

06493120

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to telecommunications systems and methods, and more particularly, to optical telecommunications systems and methods, and even more particularly to optical fiber-delay line buffers that incorporate a void filling procedure to minimize gaps in optical transmissions, for use with fixed and variable length synchronous and asynchronous optical data packets.
BACKGROUND OF THE INVENTION
Telecommunications providers have increasingly moved to optical fiber based networks. Fiber optics telecommunications networks require optical signal processing means, including optical switches or optical routers, at the nodes of the optical network to orient incoming optical signals and select the appropriate output channel. These optical switches or routers are designed to prevent packets of data from colliding because more than one packet has arrived at an output at the same time. Optical switches include buffers to aid in processing the optical data packets through the optical switch.
Conventional optical switching systems exist that are designed to prevent optical data packets from colliding during processing. However, these optical switching systems have failed to address all potential optical data packet configurations, including both synchronous (i.e., time-slotted) and asynchronous, and fixed or variable length optical data packets. This presents a significant limitation because present internet protocol (IP) traffic is asynchronous, variable length traffic. One prior art system discloses an optical switch architecture-specific switching operation that performs collision-free switching on synchronous, fixed length data packets. However, this system is limited to a particular architecture optical switch that does not accommodate variable length, asynchronous optical data packets. Furthermore, this prior art system does not fill the voids or gaps associated with optical data packet transport. Another prior art system also discloses a method of switching optical data packets, however the method is limited to fixed length optical data packets and does not accommodate wave division multiplexing (WDM). Not using WDM transmission causes a significant degradation in overall system performance. Furthermore, this prior art system also fails to disclose a method of filling voids that occur in optical transport systems.
SUMMARY OF THE INVENTION
The present invention provides an improved system and method for buffering optical transmissions that substantially eliminates or reduces disadvantages and problems associated with previously developed optical buffering systems and methods for use in fiber optic data packet transmission systems.
More specifically, the present invention provides a system and method for filling voids between optical signals during switching in an optical telecommunications system. The optical switch includes an optical buffer with a series of output fibers, where each output fiber includes a number of wavelengths, and a series of delay lines for inducing unique delays into incoming optical signals. The optical switch also include a void filling and scheduling software program resident in memory and executable by a processor. The memory also includes the wavelength, position in time, duration for each void between previously scheduled optical data packets. As a new optical data packet arrives at the optical switch, the void filling and scheduling software program will calculate the available delay for each delay line as measured from the arrival time of the new optical signal and will schedule the new optical signal within a particular void if (1) one of the available delays falls within the position in time of one of the voids and (2) the duration of the new optical signal measured from the particular available delay fits within the duration of that void.
If the new optical data packet will not fit within any of the existing voids (either because no delay coincides with the existing voids or because the space in a coincident void is not large enough to accommodate the new optical data packet), the void filling and scheduling software program will use a conventional scheduling routine to schedule the new optical data packet on an output fiber. If a new void is created during the conventional scheduling, the program can store this void in memory and attempt to fill the new void along with the previously unfilled voids as new data packets arrive.
The present invention provides an important technical advantage by filling the time gaps between optical data packets that inherently result during optical switching of optical data packets for non-uniform buffers used in conjunction with synchronous traffic and for asynchronous traffic regardless of whether the buffers are uniform or non-uniform.
The present invention provides another technical advantage by providing an improved optical buffer that can perform void filling for optical data packet that are asynchronous or synchronous, variable length or fixed length.
The present invention provides still another technical advantage by providing an improved optical buffer that can perform void filling for non-uniform buffers that virtually appear larger than equivalent uniform buffers. This increases the system performance for the same hardware, while also filling gaps between optical signals that arise.
The present invention provides another technical advantage by providing an optical buffer that is independent of the optical switch architecture and can provide the buffering for fixed/variable length optical data packets, synchronous/asynchronous optical data traffic mode for various optical switches.
The present invention provides yet another technical advantage by providing a void filling buffer and method of buffering that work equally well for both standard and wave division multiplexing optical transmission systems.
The present invention provides still another technical advantage by improving the performance of fiber delay line optical buffers under asynchronous, variable length traffic without increasing the buffer depth or size.


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A Flexible Cross-Connect Network Using Multiple Optical Carriers, by G. Depovere, et al. of Philips Research Laboratories, The Netherlands and N. Wauters, et al. of IMEC-LEA, University of Gent, Belgium (4 pgs.).

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